1. Field of the Invention
This invention relates to an apparatus for detecting a condition of the burning in an internal combustion engine.
2. Description of the Related Art
It is known to detect a condition of the burning in an internal combustion engine on the basis of the rotational speed of the engine. In general, a timing of the detection of a burning condition is set to a fixed crank angle. At this detection timing, the rotational speed of the engine is calculated. Also, it is known to detect a condition of the burning in an internal combustion engine on the basis of the pressure within a cylinder of the engine.
A typical internal combustion engine has an exhaust passage provided with a catalytic converter for reducing harmful emission. The catalytic converter becomes sufficiently active when being warmed up.
There is a known technique for quickly warming up a catalytic converter after an engine is started. The known technique has a step of greatly retarding a spark timing (an ignition timing) from normal one after the start of the engine. The retardation of the spark timing causes a greater amount of energy (unburned gas) escaping from cylinders to an exhaust passage, an increase in the temperature of exhaust gas, and the burning of unburned gas in the exhaust passage which warm up the catalytic converter.
In an internal combustion engine, the crank-angle timing of the burning depends on the spark timing. In cases where the rotational speed of the engine is calculated at a timing of a fixed crank angle independent of the spark timing, the calculated engine speed tends to be lower in accuracy for the detection of a burning condition when the spark timing is greatly regarded from normal one.
Japanese patent application publication number 11-315741 discloses an ignition timing controller of an internal combustion engine which is capable of suppressing the generation of carbon monoxide (CO), hydrocarbon (HC), and others in the exhaust gas while improving a catalytic-converter warm-up efficiency after the start of the engine. The controller in Japanese application 11-315741 includes an ECU (electronic control unit). After the start of the engine, the ECU retards the ignition timing to quickly warm up a catalytic converter. The ECU cancels the retardation of the ignition timing after the fuel injection rate determined by air-to-fuel ratio feedback control changes from an increased value to a decreased value.
U.S. Pat. No. 5,604,303 corresponding to Japanese patent application publication number 7-119530 discloses a combustion condition detecting system of an internal combustion engine. The system in U.S. Pat. No. 5,604,303 includes a first device for detecting the pressure in a cylinder of the engine, a second device for setting an integral range in a crankshaft angle in accordance with a rotation speed of the engine, a third device for integrating the pressure within the integral range thereby to derive an integrated value, a fourth device for judging whether or not an abnormal combustion occurs in the cylinder by comparing the integrated value with a reference value, and a fifth device for issuing an alarm when the fourth device judges the occurrence of the abnormal combustion. In a lower engine speed side near the idling speed, the integral range is set to appear after a given crank angle position where the pressure in the cylinder exhibits the maximum.
Japanese patent application publication number 7-119531 discloses an apparatus for detecting a condition of the burning in an internal combustion engine. The apparatus in Japanese application 7-119531 includes an in-cylinder pressure sensor for detecting the pressure within a cylinder of the engine. The detected in-cylinder pressure is integrated for a specified crank-angle interval xe2x80x9cAxe2x80x9d after ignition. The after-ignition integration-result value is denoted by SA. In addition, the detected in-cylinder pressure is integrated for a specified crank-angle interval xe2x80x9cBxe2x80x9d before ignition. The before-ignition integration-result value is denoted by SB. The value SB is subtracted from the value SA to calculate the difference xcex94S (=SAxe2x88x92SB). The difference xcex94S is compared with a reference value. When the difference xcex94S is smaller than the reference value, it is decided that abnormally burning (for example, misfire) occurs.
It is an object of this invention to provide an apparatus for accurately detecting a condition of the burning in an internal combustion engine even when the crank-angle timing of the burning is changed.
A first aspect of this invention provides an apparatus for detecting a condition of the burning in an internal combustion engine. The apparatus comprises burning-parameter controlling means for controlling a burning parameter operating on the burning in the internal combustion engine; and burning-condition detecting means for, in cases where the burning parameter is changed by the burning-parameter controlling means, sampling prescribed information for detecting a burning condition.
A second aspect of this invention is based on the first aspect thereof, and provides an apparatus further comprising a spark plug, wherein the burning parameter is a spark timing at which the spark plug generates a spark, and the burning-parameter controlling means comprises spark-timing controlling means for driving the spark plug to control the spark timing.
A third aspect of this invention is based on the first aspect thereof, and provides an apparatus further comprising a valve-timing varying mechanism, wherein the burning parameter is a timing at which an outlet valve is opened, and the burning-parameter controlling means comprises valve controlling means for controlling the timing at which the outlet valve is opened.
A fourth aspect of this invention is based on the first aspect thereof, and provides an apparatus further comprising rotational-speed detecting means for sampling information related to a rotational speed of the internal combustion engine, wherein the burning-condition detecting means comprises means for sampling the information related to the rotational speed of the internal combustion engine at a prescribed timing and in response to the burning parameter, and means for detecting the burning condition in response to the sampled information related to the rotational speed of the internal combustion engine.
A fifth aspect of this invention is based on the first aspect thereof, and provides an apparatus further comprising in-cylinder pressure detecting means for sampling information related to a pressure within a cylinder of the internal combustion engine, wherein the burning-condition detecting means comprises means for sampling the information related to the pressure within the cylinder of the internal combustion engine at a prescribed timing and in response to the burning parameter, and means for detecting the burning condition in response to the sampled information related to the pressure within the cylinder of the internal combustion engine.
A sixth aspect of this invention is based on the fourth aspect thereof, and provides an apparatus further comprising difference calculating means for calculating a rotational speed difference on the basis of the rotational speed detected by the rotational-speed detecting means, and reference-value calculating means for calculating a reference value of the burning condition on the basis of the rotational speeds of respective cylinders of the internal combustion engine which are detected by the rotational-speed detecting means, wherein the burning-condition detecting means comprises means for detecting the burning condition in response to the reference value calculated by the reference-value calculating means and the rotational speed difference between successive cylinders of the internal combustion engine which are calculated by the difference calculating means.
A seventh aspect of this invention is based on the sixth aspect thereof, and provides an apparatus wherein the rotational speed difference calculated by the difference calculating means is equal to a difference between a minimum rotational speed and a maximum rotational speed detected by the rotational-speed detecting means in one combustion cycle.
An eighth aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the burning-condition detecting means executes detecting the burning condition only in a given time interval after the internal combustion engine is started.
A ninth aspect of this invention is based on the first aspect thereof, and provides an apparatus further comprising an air-to-fuel ratio sensor for detecting an air-to-fuel ratio of an air-fuel mixture in the internal combustion engine, wherein the burning-condition detecting means executes detecting the burning condition only in a given time interval from a moment of start of the internal combustion engine to a moment of activation of the air-to-fuel ratio sensor.
A tenth aspect of this invention is based on the first aspect thereof, and provides an apparatus further comprising means for controlling an air-to-fuel ratio of an air-fuel mixture in the internal combustion engine in response to the burning condition detected by the burning-condition detecting means.
An eleventh aspect of this invention provides an apparatus for detecting a condition of the burning in an internal combustion engine in which a spark timing is variable. The apparatus comprises first means for detecting a timing of a latest spark in the engine; second means for detecting a rotational speed of the engine at a timing which depends on the latest-spark timing detected by the first means; and third means for detecting a condition of the burning in the engine in response to the rotational speed detected by the second means.
A twelfth aspect of this invention provides an apparatus for detecting a condition of the burning in an internal combustion engine in which a spark timing is variable. The apparatus comprises first means for detecting a timing of every spark in the engine; second means for detecting a rotational speed of the engine at a timing depending on the timing of every spark which is detected by the first means; third means for inhibiting the second means from detecting a rotational speed of the engine twice or more with respect to the timing of every spark which is detected by the first means; and fourth means for detecting a condition of the burning in the engine in response to the rotational speed detected by the second means.